arXiv subjects

Santiago Pérez-Hoyos

Publications and source records attributed to Santiago Pérez-Hoyos.

6 recordsLinked to original sources

arXiv2026

Cloud and ammonia vertical profiles in the equatorial atmosphere of Jupiter determined from visible to near-IR observations made by VLT/MUSE, Cassini/VIMS, IRTF/SpeX and Juno/JIRAM

We present a combined cloud/ammonia model for Jupiter's equatorial atmosphere from 0.1 to 10 bar, consistent with observations made at a range of observation geometries from 0.35 to 5.15 $μ$m by VLT/MUSE, Cassini/VIMS, IRTF/SpeX and Juno/JIRAM. Our cloud model has three components: 1) an optically-thick lower cloud (radius $r$$\sim$$10$ $μ$m) at 1-2 bar; 2) an optically-thin upper cloud ($r$$\sim$$10$ $μ$m) at $\sim$0.55 bar; and 3) a layer of blue-absorbing chromophore particles ($r$$\sim$$0.2$ $μ$m) situated within the main lower cloud. The ammonia profile is intimately linked with the cloud profile with the lower cloud coinciding with an initial drop in ammonia abundance and the upper cloud coinciding with the ammonia condensation level. The large lower cloud particles are highly scattering at visible wavelengths, allowing sunlight to scatter through the clouds and be Rayleigh-scattered from the deep atmosphere. At 5 $μ$m, the lower cloud particles are found to be more absorbing, with the belt/zone differences mostly accounted for by changes in the single-scattering albedo of these particles and secondarily by changes in the cloud opacity. The spectral properties of these lower cloud particles are possibly consistent with a component of water ice. The upper cloud particles need a distinct absorption band near 3 $μ$m, possibly consistent with a component of ammonia ice. We note that we do not need a separate upper-level photochemical haze in our model. Instead, we find that the features seen at methane-absorbing wavelengths are caused by variations in the opacity and vertical extent of the upper cloud layer.

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arXiv2026

Information content on Venusian aerosols in VIRTIS-M infrared data

Venus presents a complex cloud structure with aerosol particles of different sizes located mainly between 48 km and 70 km in altitude. However, the number of free parameters that can describe such a cloud structure is usually overwhelming, and a number of simplified parameterizations are commonly assumed. In this work, we re-analyze the information content on aerosol vertical distribution provided by the nightside infrared data collected by VIRTIS instrument onboard Venus Express. Starting from Haus et al. (2013) aerosol vertical distribution description, we use the archNEMESIS radiative transfer code and retrieval suite together with the Bayesian inference tool Multinest to compute the evidence supporting different models based on alternative choices of model parameters. This study analyzes locations at three different regions: mid-latitudes, the so-called cold collar, and the South Polar Vortex. We use a data cube that covers all of these regions simultaneously and additional observations distributed throughout the Venus Express mission. We find that these observations provide significant information about the peak particle number density, base altitude and layer thickness of aerosol modes 2, 2' and 3 when individual parameters are retrieved - a more informative description than the scaling `mode factors' often used in similar retrievals. Including mode 1 in our models, however, does not provide a significant increase of Bayesian evidence. Our retrieved cloud and temperature profiles are in general agreement with previous studies, although we find higher cloud tops in the South Polar Vortex locations. This initial computing effort provides an optimal parameterization that will allow us to study in greater detail the instantaneous horizontal cloud and temperature structure from the entire VIRTIS-M infrared database, which we will discuss in a forthcoming paper.

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arXiv2026

Colour changes of Jupiter's Oval BA through microphysical modelling

Jupiter's Oval BA undergoes recurrent colour changes whose physical origin remains uncertain. Radiative transfer retrievals indicate that these changes occur in the upper chromophore haze of the vortex annulus, around and above the 0.2-bar level, and are primarily associated with a decrease in optical depth, with no significant change in particle size or haze altitude. We apply a one-dimensional microphysical model to this haze layer, constrained by the retrieved aerosol properties of the red annulus in 2016 and the whiter annulus in 2020, and use it to reproduce the observed colour-change timescale of approximately 0.5 years. Our results indicate that this transition is best reproduced by changes in tropospheric vertical transport within a subsiding annulus, corresponding to preferred downwelling velocities of order $10^{-4}-10^{-3}$ m s$^{-1}$ at chromophore-bearing pressures. These small vertical velocities may help explain why no clear dynamical signature has yet been identified.

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arXiv2026

A Processing Workflow for Cassini VIMS Jupiter Cubes

We present a calibrated catalog of Cassini Visible and Infrared Mapping Spectrometer (VIMS) observations of Jupiter, together with the processing workflow used to generate the final publicly available products. Starting from the raw VIMS cubes, the workflow produces radiometrically consistent multi-extension FITS files and includes a revised visible-channel calibration, a revised infrared-channel calibration that resolves a subset of problematic cases not satisfactorily treated by the standard ISIS pipeline, corrections for pointing-related misalignments between spectral cubes and geometric backplanes, and customized dark signal correction strategies. The final products include calibrated spectral cubes together with geometry backplanes and wavelength information for subsequent scientific analysis. We assess the consistency of the calibrated products through internal validation tests and comparisons with independent reference spectra from the literature. The resulting products provide a uniform and validated data set of Cassini VIMS Jupiter observations for community use. The full catalog is available as a public data set at Zenodo: doi:10.5281/zenodo.19223781.

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arXiv2019

Spatial distribution of Jovian clouds, hazes and colors from Cassini ISS multi-spectral images

The Cassini spacecraft made a gravity assist flyby of Jupiter in December 2000. The Imaging Science Subsystem (ISS) acquired images of the planet that covered the visual range with filters sensitive to the distribution of clouds and hazes, their altitudes and color. We use a selection of these images to build high-resolution cylindrical maps of the planet in 9 wavelengths. We explore the spatial distribution of the planet reflectivity examining the distribution of color and altitudes of hazes as well as their relation. A variety of analyses is presented: a) Principal Component Analysis (PCA); b) color-altitude indices; and c) chromaticity diagrams (for a quantitative characterization of Jupiter "true" colors as they would be perceived by a human observer). PCA of the full dataset indicates that six components are required to explain the data. These components are likely related to the distribution of cloud opacity at the main cloud, the distribution of two types of hazes, two chromophores or coloring processes and the distribution of convective storms.

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arXiv2016

The Great Saturn Storm of 2010-2011

In December 2010, a major storm erupted in Saturn's northern hemisphere near 37 degree planetographic latitude. This rather surprising event, occurring at an unexpected latitude and time, is the sixth "Great White Spot" (GWS) storm observed over the last century and a half. Such GWS events are planetary-scale atmospheric phenomena that dramatically change the typically bland appearance of the planet. Occurring while the Cassini mission was on-orbit at Saturn, the Great Storm of 2010-2011 was well-suited for intense scrutiny by the suite of sophisticated instruments onboard the Cassini spacecraft as well by modern instrumentation on ground-based telescopes and onboard the Hubble Space Telescope. This GWS erupted on December 5th and generated a major dynamical disturbance that affected the whole latitude band from 25 deg to 48 deg N. Lightning events were prominent and detected as outbursts and flashes at both optical and radio wavelengths. The activity of the head ceased after about seven months, leaving the cloud structure and ambient winds perturbed. The tops of the optically dense clouds of the storm's head reached the 300 mbar altitude level where a mixture of ices was detected. The energetics of the frequency and power of lightning, as well as the estimated power generated by the latent heat released in the water-based convection, both indicate that the power released for the storm was a significant fraction of Saturn's total radiated power. The effects of the storm propagated into the stratosphere forming two warm airmasses at the 0.5-5 mbar pressure level altitude. Related to the stratospheric disturbance, hydrocarbon composition excesses were found. The decades-long interval between storms is probably related to the insolation cycle and the long radiative time constant of Saturn's atmosphere, and several theories for temporarily storing energy have been proposed.

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